The present invention is directed toward capacitively coupled plated antennas for use in wireless communications devices and, more particularly, toward capacitively coupled plated antennas for Bluetooth or GPS (Global Positioning System) applications.
Wireless communications devices are widely used for both wireless voice and data communications. Such wireless communications devices typically include, but are not limited to, analog and digital cellular phones, wireless phone handsets, wireless communicators, personal computers and laptops equipped with wireless modems, Personal Digital Assistants (PDAs), and other wireless electronic devices. The development and refinement of wireless communications devices continues to occur at an extremely rapid pace. Some of the problems associated with the development and refinement of wireless communications devices relate to the cost, size and complexity of the device.
As wireless communications devices become smaller and smaller, as typically occurs with each new generation cellar phone, the allotted space within the wireless communications device must continually be more efficiently utilized. Such spacial concerns typically involve considerations relating to the size of the antenna and the size and layout of elements on the printed circuit (PC) board. In most wireless communications devices, and in particular cellular phones, various internal components of the device are mounted to the PC board housed within the device. Antennas can be internal to the wireless communications device or external. External antennas are generally obtrusive, while internal antennas typically require PC board space. Further, since both internal and external antennas are directly connected to the RF (Radio Frequency) feed, they may require lumped element matching components for antenna impedance matching purposes which occupy further PC board space.
For example, for short-range applications, such as Bluetooth applications, an external stub antenna may be utilized that is printed on the same flex-film substrate on which there is the main triple-band antenna. Antennas, such as a printed inverted-F antenna, may also be directly printed on the PC board in Bluetooth applications. A drawback of these antennas is that they occupy a volume of the PC board, and require a window on the PC board around the antenna where no metallic objects are permitted in order to radiate efficiently. In long-range applications, such as GPS applications, surface mount printed inverted-F antennas may be utilized, as well as external quadrifilar helix antennas, external patch antennas, and internal notch antennas. However, each of these different types of antennas exhibits the same problems as previously noted. The external antennas are obtrusive and the internal ones require additional PC board space, and since each antenna is directly connected to the RF feed they may require lumped element matching components occupying further PC board space.
The present invention is directed toward overcoming one or more of the above-mentioned problems.
The present invention overcomes the above-described problems, and achieves other advantages, by providing an internal antenna that requires minimal PC board space and is not directly connected to any components in the wireless communications device. The general configuration of the antenna is such that it is self-matched and, accordingly, no element matching components are required.
According to an exemplary embodiment of the present invention, an antenna is provided for use in a wireless communications device having receive and transmit circuitry within a housing for receiving and transmitting radio signals. The antenna is built into the housing of the wireless communications device. A coupling plate is provided within the housing for transferring received and transmitted radio signals between the antenna and the receive and transmit circuitry. The coupling plate is connected to the receive and transmit circuitry and spaced from the antenna by a distance h1, such that the received and transmitted radio signals are transferred between the antenna and the receive and transmit circuitry only by capacitive coupling between the antenna and the coupling plate.
In one form, the distance h1, between the coupling plate and the antenna is equal to 1-3 mm. This enables the inventive antenna to be utilized for short-range applications using wireless communications protocol, such as the well known Bluetooth protocol that defines a radio interface in the 2.4-2.485 GHz frequency band of operation, and also for long-range GPS applications having an operating frequency of 1.57542 GHz with some operating bandwidth for tolerance.
In another form, the antenna is formed on an inner surface of the housing and, further, is formed by either plating, vacuum evaporation, adhering a metal plate onto the inner surface of the housing, or other conventional means. To avoid having to incorporate antenna impedance matching components into the device, the geometry of the antenna is such that it is impedance matched to the receive and transmit circuitry.
The antenna may include first and second antenna elements, with the first antenna element formed on the housing at a position corresponding to the coupling plate. The first antenna element and the coupling plate typically have the same geometric shape, consisting of a square, a circle, a triangle, or any other geometric configuration suitable for an appropriate wireless application.
Wireless communications devices typically include a PC board having the receive and transmit circuitry thereon, as well as other components and elements. In one form, the coupling plate is spaced from the PC board by a distance h2. This enables RF circuit components to be placed on the PC board underneath the coupling plate. In a preferred form, the distance h2 between the PC board and the coupling plate is equal to 1-4 mm.
It is an object of the present invention to provide a plated antenna for a wireless communications device which occupies minimal PC board space.
It is a further object of the present invention to provide an antenna for wireless communications device which is neither connected to RF nor ground.
It is still a further object of the present invention to provide an antenna for a wireless communications device having reduced cost and complexity.
It is yet a further object of the present invention to provide an antenna for a wireless communications device which does not require additional impedance matching element components.
Other aspects, objects and advantages of the present invention can be obtained from the study of the application, the drawings, and the appended claims.